PACIFIC BEACH — Lunchtime drivers passing through the intersection of Balboa Avenue and East Mission Bay Drive — cited in a 1990s report as San Diego’s busiest intersection — came upon the ingredients for a perfect storm today, as far as traffic congestion is concerned. First of all, the intersection’s four-way traffic signals were not functioning properly, only showing the blinking red light which signals to drivers that they should treat it as a four-way stop, taking turns passing one set of cars at at time. Then, heading west as Balboa becomes Garnet Avenue, the remnants of what appeared to be a single-car fire were being mopped up by firefighters at about 12:20 p.m. The entire front of the white car, which was in the left lane going eastbound on Garnet Avenue near Rose Creek Cottage, was badly burned. Police allowed cars to pass slowly in the right side of the eastbound lane and drivers remained calm in spite of the congestion as of 12:30 p.m.